Hitherto, in a refrigeration cycle system used for air conditioners, refrigerating/freezing showcases, and the like, there is a need to adjust a flow rate of a circulating refrigerant for the purpose of a highly efficient operation while stabilizing a cooling capacity and keeping a constant superheat degree. Then, in order to highly accurately perform the adjustment at that time, an electric valve which is an electric expansion valve for operating a valve body by a stepping motor corresponding to an expansion valve for a flow rate control has been widely used. Further, there is also known an electric valve such as a three-way valve (a passage switching valve) of switching a refrigerant flow direction or a shut valve of allowing or interrupting a flow of a refrigerant by opening or closing a refrigerant passage using a stepping motor.
However, in the above-described electric valve using the stepping motor, it is general to control an opening degree by using an open loop control which does not have a feedback of an absolute opening degree (an actual opening degree). Further, the valve body inside the valve stops at a position at the time of the interruption of power while not returning to an initial position when the supply of power is stopped. For that reason, there is a problem in which the valve body stopping position (the absolute opening degree) cannot be accurately recognized when power is input at the next time.
Regarding the control of the above-described electric valve using the stepping motor, an initialization process (also referred to as original positioning, reference positioning, or initialization) is performed when power is normally input for the positioning of the valve body and the opening degree control is started (for example, see Patent Document 1). Here, the initialization process is a process of sufficiently rotating the stepping motor in a valve closing direction or a valve opening direction by the number of pulses exceeding a full stroke from a full open position to a full close position or vice versa, that is, the number of pulses in which a rotor of the stepping motor collides with a rotation stopper called a stopper so that its rotation is stopped. Accordingly, the initial position of the electric valve at 0 pulse or a maximum pulse is defined.